Patent US3681672A successfully refreshed from Google Patents.
US3681672A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitor overcharge protection circuit
Assignee: Rollei Werke Franke und Heidecke GmbH and Co KG
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Filing: 1971-07-01
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Granted: 1972-08-01
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Expires: 1991-07-01
Abstract
Abstract Photo flash apparatus having two storage capacitors connected in series. Normally both capacitors are charged by a voltage doubling circuit connected to an alternating current supply, to a predetermined direct current voltage across both capacitors in series. To prevent overcharging and possible breakdwon of one capacitor in case the charge on the other capacitor decreases as a result of leakage current, the invention provides a safety circuit having two resistors in series with each other and in parallel with the respective capacitors, the safety circuit having a central connection from the junction between the two resistors to the junction between the two capacitors, the central connection containing an impulse transformer which operates when the charges on the two capacitors differ by more than a predetermined amount. The output of the impulse transformer can be used to give an indication of fault or to interrupt automatically the charging of the capacitors.
Inventors
- 👤 Karl-Peter Strauss
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 09:24
CPC Classifications
H; H02; H02H; H02H7/00; H02H7/16
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
169 words
Electronic flash apparatus comprising two storage capacitors connected in series with each other to store a charge to provide power for a flash, two resistors connected in series with each other and in parallel with the two storage capacitors in such manner as to be subjected to the working voltage of the capacitors, and a bridge connection connecting a central junction between the two capacitors to a central junction between the two resistors, said bridge connection having a capacitor, an impulse transformer in parallel with such capacitor, and a break-through device becoming conductive when subjected to a predetermined difference in potential arranged in series with said transformer and in parallel with said last named capacitor, said apparatus being so arranged that when the voltage across one of said storage capacitors differs by more than a predetermined amount from the voltage across the other of said storage capacitors, said break-through device will become conductive and the bridge connection capacitor will discharge therethrough and through said transformer to activate said transformer.
Claim 2
Dependent Claim
169 words
Electronic flash apparatus comprising two storage capacitors connected in series with each other to store a charge to provide power for a flash, two resistors connected in series with each other and in parallel with the two storage capacitors in such manner as to be subjected to the working voltage of the capacitors, and a bridge connection connecting a central junction between the two capacitors to a central junction between the two resistors, said bridge connection having a capacitor, an impulse transformer in parallel with such capacitor, and a break-through device becoming conductive when subjected to a predetermined difference in potential arranged in series with said transformer and in parallel with said last named capacitor, said apparatus being so arranged that when the voltage across one of said storage capacitors differs by more than a predetermined amount from the voltage across the other of said storage capacitors, said break-through device will become conductive and the bridge connection capacitor will discharge therethrough and through said transformer to activate said transformer.
Claim 3
Dependent Claim
28 words
Flash apparatus as defined in claim 1, wherein the resistance ratios of said two resistors correspond respectively to the desired charging voltage ratios of the two storage capacitors.
Claim 4
Dependent Claim
14 words
Flash apparatus as defined in claim 1, wherein said break-through device is a diac.
Claim 5
Dependent Claim
15 words
Flash apparatus as defined in claim 1, wherein said break-through device is a glow lamp.
Claim 6
Dependent Claim
15 words
Flash apparatus as defined in claim 1, wherein said break-through device is a four-layer diode.
Claim 7
Dependent Claim
15 words
Flash apparatus as defined in claim 1, wherein said break-through device is a unijunction transistor.
Claim 8
Dependent Claim
31 words
Flash apparatus as defined in claim 1, further including means responsive to activation of said transformer for at least temporarily blocking further charging of at least one of said storage capacitors.
Claim 9
Dependent Claim
37 words
Flash apparatus as defined in claim 1, further including means responsive to activation of said transformer for at least temporarily blocking further charging of that one of said storage capacitors which is charged to the higher voltage.
Claim 10
Dependent Claim
93 words
Flash apparatus as defined in claim 1, wherein said impulse transformer has a primary winding in series with said break-through device and two secondary windings (27, 28), said two storage capacitors (1, 2) have charging circuits separately controlled by two trigger-controlled rectifier thyristors (3, 4), and each of said secondary windings (27, 28) is operatively connected through a respective individual diode (29, 30) to a trigger circuit for the respective rectifier thyristor (3, 4) in such manner that passage of trigger impulses to the corresponding thyristor (3, 4) is blocked or short circuited.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-08-01 | 1976-01-31 | 1976-08-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-01 | 1980-01-31 | 1980-08-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-01 | 1984-01-31 | 1984-08-01 | $7700.00 | Window Closed / Lapsed |